package com.lagou.sqlSession;

import com.lagou.pojo.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * 封装JDBC代码完成对数据库表的操作
 * @author: liufh
 * @create: 2021-06-28 14:32
 **/
public class SimpleExecutor implements Executor {

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InstantiationException, IntrospectionException, InvocationTargetException {
        // 1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2.获取sql语句
        //   转换sql：#{}->?    转换的过程中，还需要对#{}里的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3.获取预处理对象prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getParseSql());
        // 4.设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getTypeClass(parameterType);
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            String content = parameterMapping.getContent();
            Object o = null;
            if ("java.lang.Integer".equals(parameterType) ||
                    "java.lang.Double".equals(parameterType) ||
                    "java.lang.String".equals(parameterType)) { //普通类型
                o = params[0];
            } else {//对象类型
                //反射
                Field declaredField = parameterTypeClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                o = declaredField.get(params[0]);//入参为对象类型且为一个的情况，才取params[0]
            }
            preparedStatement.setObject(i+1, o);
        }

        // 5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        // 6. 封装返回结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getTypeClass(resultType);
        ArrayList<Object> list = new ArrayList<>();
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            list.add(o);
        }

        return (List<E>)list;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object param) throws Exception {
        // 1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2.获取insert/update/delete sql语句
        //   转换sql：#{}->?    转换的过程中，还需要对#{}里的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3.获取预处理对象prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getParseSql());
        // 4.设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getTypeClass(parameterType);
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(param);

            preparedStatement.setObject(i+1, o);
        }

        // 5.执行sql
        preparedStatement.execute();
        int count = preparedStatement.getUpdateCount();

        return count;
    }

    private Class<?> getTypeClass(String className) throws ClassNotFoundException {
        if (className != null) {
            Class<?> aClass = Class.forName(className);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：
     *  1.将#{}使用?进行替换
     *  2.解析出#{}里面的值进行存储
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }

}
